Secondary clock synchronizing mechanism



P 1951 R. B. JOHNSON ETAL SECONDARY CLOCK SYNCHRONIZING MECHANISM FiledApril 25, 1946 4 Sheets-Sheet l R. BY J'SHKEE N BY E.F. GEIGER ATTORNEYp 1951 R. B. JOHNSON ETAL SECONDARY CLOCK SYNCHRONIZING MECHANISM FiledApril 25, 1946 i 4 Shts-Sheet 2 sw R R 0 E a T G N NHE .R w 0 N n -A REP 1951 R. B. JOHNSON ETAL SECONDARY CLOCK SYNCHRONIZING MECHANISM FiledA ril 25, 1946 4 Sheets-Sheet 5 p 1951 R. B. JOHNSON ET AL 2,566,940

SECONDARY CLOCK SYNCHRONIZING MECHANISM Filed April 25, 1946 4Sheets-Sheet 4 INVENTORS RB. JOHNSON E.F GEIGER Patented Sept. 4, 1951SECONDARY CLOCK SYNCHRONIZING MECHANI Reynold B. Johnson and Edward F.Geiger, Binghamton, N. Y., minors to International Business MachinesCorporation, New York, N. Y., a corporation of New York ApplicationApril 25, 1946. Serial No. 664,933

16 Claims. (Cl. 58-26) This invention relates to time-keeping apparatusand more particularly to secondary clocks and similar time-keeping unitsof the type normally driven by individual driving motors, for example, asynchronous A. C. motor, and, which are automatically regulated atselected intervals in response to time signals transmitted from a sourceof correct or standard time.

An object of the invention is to provide secondary time-keepingapparatus of the type referred to which is of improved construction andarrangement of parts.

A further object is to provide a novel form of secondary clockconstruction which includes an improved structural combination andarrangement of parts for advancing the clock, when slow, to a.chronological position coincident with standard time.

Other objects of the invention will be pointed out in the followingdescription and claims and illustrated in the accompanying drawings,which disclose, by way of example, the principle of the invention andthe best mode, which has been contemplated, of applying that principle.

In the drawings:

Fig. 1 is a transverse vertical sectional view through a secondary clockconstructed in accordance with the present invention, the outline of theface and hands of the clock being shown by dot-and-dash lines, and theplane of the section being indicated by th line I--l of Fig. 2;

Fig. 2 is a vertical longitudinal sectional view taken on the line 2-2of Fig. 1, with the clock operating mechanism appearing in verticalelevatlon;

Fig. 3 is avertical elevational view of'the clock mechanism and showingthe side thereof opposite to that shown in Fig. 2;

Fig. 4 is a transverse vertical sectional view through the clockmechanism taken on the line 4-4 of Fig. 2;

Fig. 5 is a detail elevational view showing the rear face of the clockgear which drives the minutes hand;

Fig. 6 is an enlarged plan sectional view of the clock mechanism takenon the line 6-6 of Fig. 1;

Fig. '7 is an enlarged detail perspective view showing the operativerelationship between the seconds and minutes stop pawls with respect tothe seconds stop arm and'the minutes stop stud, certain parts of theclock mechanism not forming a direct part of this relationship beingomitted for the purposes of clarity;

Fig. 8 is a fragmentary transverse vertical sec- 2 tional view of theclock mechanism taken on the line 88 of Fig. 2;

Fig. 9 is a detail elevational view showing the time-correcting diskwith related parts attached thereto;

Figs. 1Q to 13 inclusive are fragmentary vertical sectional views of theclock mechanism each being taken on the same plane as Fig. 1, and theviews showing the different relative positions occupied by the partsduring the several operating steps of a time-correcting operation.

Referring now in detail to the construction 11- lustrated, the referencenumeral I0 indicates, in its entirety, one preferred form of anautomatically regulated secondary clock constructed in accordance withthe present invention. As shown. the clock l0 comprises the usual faceplate ll, seconds hand l2, minutes hand l3, and hours hand l4. Parallelfront and rear support plates of the clock are indicated at l5 and I6,respectively, and they are suitably secured in their predeterminedspaced relationship by pillars ll. An electric driving motor for theclock is indicated by the character l8, and is shown as being supportedby the rear plate IS. The remaining operating mechanisms of the clockare mounted between the plates I5 and t6. as will presently appear.

The motor I8 is preferably of the self-startin synchronous type and isadapted to be driven at its designed time rate from the availablefrequency-regulated A. C. light and power line. The output shaft 20 ofthe motor is operatively connected by a pinion 2| to a seconds drivinggearv 22 which is rotatably mounted on a seconds shaft 22. With themotor operating from the available A. C. power line, the seconds gear 22will be driven at the rate of one R. P. M.

The seconds shaft 23 is rotatably supported at its rear end by the rearsupport plate 18 and is rotatably supported at its forward end in aminutes sleeve 24, the latter being in turn journalled in an hourssleeve 25 which is rotatably supported within a bearing opening in thefront support plate IS. The seconds shaft 23 is rotated from the secondsgear 22 through a suitable friction drive connection indicated at 26.This operative connection is made through 2. seconds driving pinion 21which is rotatively mounted on the shaft 23 and is fixed to the rearface of the seconds gear 22. The pinion 21 is connected by the frictionconnection 26 with a. collar 28 fixed to the seconds shaft 23. As willbe apparent from an examination of Figs. 2, 3, and 6, the connection 26comprises a spider-like spring member having a base element fixed to therearward face of the driving pinion 21 and having spring fingersextending outwardly and rearwardly therefrom and frictionally engagingthe forward face of the collar 28. Thus, normally the seconds gear 22and the seconds shaft 23 both operate at their regular speed of one B.P. M. However, the friction drive connection 26 permits relativemovement between the seconds gear 22 and seconds shaft 23 when requiredfor time correcting operations, as will later appear.

Formed as an integralpart of the collar 28 is an outwardly extendingseconds stop arm 29. The seconds hand I2 is connected to the opposite orforward end of the seconds shaft 23. Thus, the stop arm 29 and hand l2move together with the seconds shaft 23 and the arm 29, therefore,occupies a definite angular position with respect to the hand I 2 forany given time indicating position of the latter. It is noted that inFigs. 1, 3, 6, 7, 8, 1'0, and 11, the stop arm 29 is shown in theangular position it occupies when the seconds hand I 2 indicatesfifty-five seconds after the even minute. Fig. 12 shows the position ofthe arm 29 when the seconds hand 12 is at the even minute position whichmay also be referred to as the zero or sixtieth second position.

The seconds driving pinion 21 is in mesh with gear 3| which has asuitable friction driving connection 32 with a concentric hub 33 fixedto a shaft 34, the latter being Journalled at its two ends in the twoclock support plates I and I6, respectively, and being arranged inspaced parallel relation with respect to the seconds shaft 23 andminutes sleeve 24. A pinion 35 is also fixed to the shaft 34 and mesheswith a minutes drive gear 36 fixed to the minutes sleeve 24. Fig. 5shows the gear 36 apart from other elements of the latter at its propertime rate through the conventional gear reduction train composed of thegears 42, 43, 44, and 45 (see Figs. 2, 3, 4, and 6). As shown, the hourshand I4 is secured to the forward end of the hours sleeve 25.

A time-correcting disk 46 is rotatably mounted on the seconds shaft 23at the rear of the minutes gear 36 and is kept in axially spacedrelation with respect to the latter by a forwardly extending hub 41 (seeparticularly Figs. 6 and 9). The timecorrecting disk 46 is normally heldagainst rota- 7 tion at a predetermined angular position thereof theclock. As shown, the minutes indicating hand I3 is secured to theforward end of the minutes sleeve 24. The gears 21, 3|, 35, and 36 aredesigned to provide for the driving of the minutes sleeve 24 at itscorrect time rate of one R. P. H. from the seconds gear 22 and motor l6.The friction driving connection 32 between the gear 3| and hub 33permits relative motion between the constantly rotating seconds gear 22and the minutes gear 36 and minutes hand I3 when necessary during timecorrecting periods, as will presently appear.

ProjecLng from the forward side of the minutes gear 36, is a minutesstop stud 37 which occupies a definite angular position for eachtime-indi cating position of the minutes hand l3 (see Figs.

1, 3, 5, 6, 7). Also fixed to the minutes gear 36 and on the rear facethereof, is a spring finger 38. As shown, the finger 38-is fixed at oneend thereof to the gear by suitable pins 39 and the remaining portionsof the spring element project away from the rear face of the gear andare normally held in such position by the inherent spring force in thefinger 38. The finger 38 terminates at its outer or free end in an outerabutment edge or face 4|. The purpose of the spring finger 36 willbedescribed in detail hereinafter. The minutes stop stud 31 and the finger38 are shown in Figs. 1, 4, 5, 6, '7, 10, 11, and 12 in the positionthey occupy when the minutes hand l3 indicates fifty minutes past theeven hour. In Fig. 13, the stud 31 and finger 38 are shown in theposition they occupy at the even hour position, which may also bereferred to as the zero or sixtieth minute position.

The hours sleeve 25, which, as stated, is journalled on the minutessleeve 24, is driven from by means of an upper hooked end 48 of apivoted stop pawl 49 (Fig. 1) engaging a tail portion 5| of an advancingpawl 52, the latter being pivoted on the disk by a suitable pin 53projecting from the rear side of the disk and adjacent the peripherythereof. The stop pawl 49 is pivoted on a fixed rod 54 supported at itsends by the front and rear plates 5 and I6, re-

spectively. When the hook 48 engages the tail 5| as shown in Figs. 1 and10, the disk 46 is thus held against rotation in the predeterminednormal angular position referred to. A tension spring 64 connecting adepending arm 65 of the stop pawl 49 and a fixed rod 66 carried by theplates l5 and I5. constantly urges the pawl 49 clockwise as viewed inFig. 1 and thereby holds the hook 48 and tail 5| of the dog 52 inengagement at the predetermined normal angular position of the disk 48.

The disk 46 is further retained in its said normal angular position by astop-actuating and detent lever 55 which includes a depending arm 56having a wedge-shaped lower end 51 fitting within a correspondinglyshaped notch 58 in the periphery of the disk when the disk is in itssaid predetermined normal position. The stop actuating lever 55 is fixedon a shaft 59 which is journalied at its ends in the support plates l5and I6 (see Figs. 6 and '1). A tension spring 6| connecting an upwardlyextending arm 62 of the stop lever 55 and a fixed rod 63 held at itsends by the plates l5 and I6, constantly urges the wedgeshaped lower end51 against the periphery of the disk 46 and thereby holds such end 51within the notch 58 and retains the disk in its predetermined normalposition.

Projecting from the forward face of the disk 46 and into the path of theouter edge 4| of the spring finger 38, which is carried by the minutesgear 36, is a clock advancing stud 61. The stud 61 and spring finger 38comprises the two coacting parts of a one-way coupling between theminutes gear 36 and the time-correcting disk 46. During normaltime-keeping operation when the disk 46, and likewise its stud 61 remainstationary and the minutes gear 36 and spring finger 33 are movedclockwise at the regular time rate of one R. P. H., as previouslydescribed, the advancing stud 61 will not interfere with such normaltimekeeping movement of the clock gear 36. During such movement, theouter, or rear, face of the finger 38, at points spaced inwardly fromthe outer edge 4| thereof, will first engage the outer end of the stud61; and, as the gear 36 continues to move clockwise, the outer face ofthe finger will simply wipe or slide, over the end of stud 61 which willonly result in the outer portions of the finger being moved inwardlyagainst its inherent spring force and toward the face of the gear 36 andconsequently the normal clockwise movement of the gear will not beretarded. When the outer free edge 4| of the finger 38 clears the stud61. the linear will then snap outwardly from the face of the gear 36 andback to its normal position. However, as will appear more fullyhereinafter, the disk 46 is released periodically to effect atime-correcting operation and the disk then rotates clockwise at a ratematerially faster than the normal rate of the minutes gear. The stud 61may then overtake and engage the edge 4| of the spring 38 and therebyadvance the gear 36 at the speed of the disk 46.

A biasing spring 68 (see Fig. 9) has one end thereof engaging the pawl52 and is fixed at its other end to the time-correcting disk 46, thepurpose of the spring 68 being to constantly urge the advancing pawl 52to move in a clockwise direction, as viewed in Figs. 1, 9, and 10. Thus,when the stop pawl 48 is moved counterclockwise, in a manner which willbe presently explained, to release its upper hooked end 48 from the tailportion 5| of the advancing pawl 52, the spring 68 will move the pawl 52about it pivot 53 and thereby effect locking or clutching engagement ofits outer hooked end 68 with the teeth of a ratchet wheel Ill. Theratchet wheel I is rotatably mounted on the seconds shaft 23 and isfixed to the forward side of the seconds gear 22 and rotates constantlytherewith so that when the advancing pawl 52 is released by outwardmovement of the stop pawl 49, and the advancing pawl 52 thus engages theratchet ID, the disk 46 is clutched to the ratchet I0 and is rotatedthereby at the speed of the seconds gear 22. As will appear more fullyhereinafter, after the stop pawl 48 is moved counterclockwise to releasethe advancing pawl 52 and the disk 46, the spring 64 will return thestop pawl to the position shown in Figs. 1, 10, 12, and 13, at whichtime it hooked end 48 will be in the path of the tail 5| of the pawl 52and so that it will be engaged by the tail 5| as the disk 46 completesone revolution. This engagement of the tail 5| and hooked end 48 willresult in the pawl 52 being pivoted. counterclockwise (as viewed inFig. 1) against the force of its biasing spring 68 and therebydisengaging the advancing pawl 52 from the teeth of the ratchet wheelIll and stopping the disk 46 at its said predetermined normal angularposition. The pawl 52, ratchet I0, and pawl 48 may be considered aselements of a one-revolution clutch which provides a driving connectionbetween the driving gear 22 and the time-correcting disk 48. As statedpreviously, the wedge-shaped end 51 fits fully within the notch 58 atthe normal angular position of the disk 46 and thereby aids in holdingthe disk at such position.

A stop pawl I2 is rotatably mounted on the shaft 58 and in substantiallythe same transverse plane as the previously described stop arm 28 whichis fixed to the seconds shaft, and a second stop pawl 13 (see Figs. 4,6, and 7) is rotatably mounted on the shaft 58 in substantially the sameplane as the path of movement of the stop stud 31 on the minutes gear36. Associated with and mounted alongside the stop pawl 12 is a controlarm I4 fixed to the shaft 58, and associated with the stop pawl I3 is asecond control arm I5 which is also fixed'tothe shaft 58. The arm I4 isprovided with a lug I6 extending under its associated pawl I2 and atension spring 11 connecting the arm I4 and a .tail I8 on the pawl I2constantly urges the pawl I2 against the lug I6 50 that the pawl I2 andassociated control arm I4 normally move together as a unit with therotation of the shaft 58. Likewise, the arm I5 is provided with a lug I8and a tension spring, 80 functions to yieldingly hold the arm I5 and itswould be struck by its related pawl.

the arm 28 and stud 31, respectively. When the time-correcting disk 46moves from it predetermined normal position, the wedge-shaped end 51 iscammed out of the notch 58 and onto the periphery of the disk 46 (seeFigs. 7 and 8). This will result in the shaft 59 and arms 14 and I5being moved counterclockwise as viewed in Figs. 1, 6, 7, 8 and 10 to 13inclusive, and clockwise as viewed in Fig. 4. The springs TI and 80 willcause the stop pawls I2 and I3 to move with their associated arms I4 and15, respectively, and to positions where the pawl I2 lies in the path ofmovement of the outer end of the arm 29 and the pawl I3 lies in the pathof movement of the stop stud 31. The construction is such that when thepawl I2 is thus moved into an intercepting or blocking position withrespect to the arm 29 and when the latter engages the pawl, the arm 29and seconds shaft 23, will be stopped at the even minute or sixtiethsecond position of the seconds hand |2. The friction connection 26permits continued movement of the seconds gear 22 when the arm 28 isthus held by the pawl I2. Also, the other pawl I8 is so arranged thatwhen it is in its intercepting 01 blocking position, it will stop thestud 31 and minutes gear 36 at the position where the minutes hand I3indicates the even hour, or which, a stated, may also be referred to asthe zero or sixtieth minute position of the hand l3. The frictionconnection 32 between the gear 3| and hub 33 permits stopping of theminutes gear and minutes hand without affecting movement of the secondsgear 22.

The spring connections between the stop pawls I2 and I3 and theirassociated arms I4 and I5 serve to prevent damage to the part in casethe stop pawls should be actuated when either the arm 29, or stud 31,occupies a position where it Thus, if

' either stop pawl I2 and I3 strikes and is thereby stopped by itsassociated arm 28, or stud 31. as such pawl is actuated, its tensionspring 11, or 80, will permit continued movement of its associated armI4, or I5, and thereby prevent damage to the parts. When the latteroccurs and the arm 28, or stud 31, moves out of engagement with itspawl, the associated tension spring will then move such pawl into itsintercepting position.

According to the illustrative embodiment, means is provided forautomatically correcting the time setting of the secondary clock at apreselected hourly time position a master clock or other source ofstandard time. The correction may be effected each hour, or duringcertain selected hours, if desired. As the frequency of the availablealternating current is closely regulated at the source, synchronousmotor driven clocks will seldom vary more than a small fraction of aminute, unless there be an interruption in the power supply or theexistence in the secondary clock of an unusual amount of friction orbinding of the working parts, such as would cause the clock to losetime. As will presently appear, the illustrative embodiment willautomatically correct for loss of time up to 59 minutes and will correctfor gain of time for a fraction of a minute.

Automatic correction is effected each hour in the illustrativeembodiment, by releasing the time-correcting disk 46 at fifty-nineminutes past the hour according to standard time. As stated previously,as soon as the advancing pawl 52 engages the ratchet I8 and the disk 46thereby begins to move, the lower wedge-shaped end 51 of the lever 55 iscammed out of its notch 58 and the sto pawls l2 and 13 are therebymoved, respectively, into intercepting or blocking positions withrespect 'to the seconds stop arm 29 and the minutes stop stud 31. Thus,the pawls l2 and I3 are moved into their intercepting ositionssubstantially simultaneously with the releasing of the disk 46.

The disk 46 is released at the fifty-ninth minute past each hour by atrigger mechanism indicated generally by the reference character 82 (seeFigs. 1, 4, and 10 to 13 inclusive) and which is operated to release thedisk under the control of a trip magnet 83 which is suitably supportedby the plates l5 and l6. The energizing of the magnet 83 cocks thetrigger mechanism and the deenergizing of the magnet trips the mechanismto release the disk at the fifty-ninth minute.

As shown in Figs. 1, 3, 4, 6, and to 13 inclusive, the trigger mechanism82 includes the armature 84 of the magnet 83 which is pivoted on a fixedrod 85 carried by the support plates l5 and 16, a laterally movable trippawl 86 pivoted by a pin 81 to an upwardly extending arm 88 of thearmature 84, and the pivoted stop pawl 49 having a depending latch plate89 adapted to coact with a latching notch 98 formed in the upperleft-hand part, as viewed in Fig. 1, of the trip pawl 86. A tensionspring 92 connecting the right-hand end of the pawl 86-and one of thepillars I'I, constantly urges the trip pawl towards the right andthereby also urges the armature 84 in a clockwise direction towards itsdeenergized position. A fixed stop rod 93 extending between the supportplates 15 and I6 coacts with an upstanding hook portion 94 on the pawl86 to limit its movement towards the right and also coacts with adepending tail portion 95 on the stop pawl 49 to limit clockwisemovement of the latter under the force of the tension spring 64. A

tension spring 96 connecting the left-hand end of the trip pawl 86 andthe fixedrod 66 urges the trip pawl 86 upward against the stop rod 93.

Time-correcting operation A time-correcting operation will be readilyunderstood from a study of Figs. 1, 4, and 10 to 13 inclusive of thedrawings. In Fig. 1, the parts are shown in the relative positionsnormally occupied between time-correcting signals. As shown, the timeindicated by the clock 18 in Fig. 1 is ten minutes and five secondsbefore 2 o'clock. For the purposes of description, it will be assumedthat an electrical time signal or impulse is received by the magnet 83from a master clock, not shown, or other source of standard time. Itwill also be assumed that the transmission of the impulse will begin amoment before the fiftyninth minute of the standard time source, forexample, one or two seconds, and that the impulse will terminate at thefifty-ninth minute, and that the secondary clock 18 is now running slowwith respect to standard time by the amount indicated in Fig. 1. Theimpulse will energize the magnet 83 and the latter will attract itsarshown in Fig. 10. As the armature 84 is attracted it movescounterclockwise and moves therewith the trip pawl 86 towards the leftand against the force of the tension spring 92. This will move thelatching notch 98 beneath the lower edge of the latch plate 89 andduring such movement the lefthand end of the trip pawl will also bemoved upward due to the force of the spring 96 and as permitted by thecam face 91 on the pawl 86 engaging the stop rod 93 and until the lowerend a; the latching plate 89 is in the latching notch 98,

As stated, the standard time signal, or impulse, terminates at thefifty-ninth minute of the mas-- ter clock or other source of correcttime, and thereby deenergizes the trip magnet 83 which permits thespring 92 to actuate the trigger mechanism and thereby release thetime-correcting disk. This trigger actuating operation can best beunderstood with reference to Fig. 11 which shows the relative positionof the parts at the moment the disk 46 is released. As the magnet 83becomes deenergized, the spring 92 pulls the trip pawl 86 towards theright. As the lower end of the latch plate 89 is engaged by theleft-hand end of the latching notch 98, the plate 89 and stop pawl 49will be moved counterclockwise by the spring 92 and to a position wherethe upper hooked end 48 thereof will release the advancing pawl 52 sothat the latter will engage the ratchet 18 under the force of the spring68, as explained previously. As the spring 92 continues to move the trippawl 86 towards the right, the cam surface. 91 which is in engagementwith the stop rod 93, cams the left-hand end of the pawl 86 downward toa point where the latching notch 98 releases the lower edge of the latchplate 89 and thereby permits the spring 64 to restore the stop pawl 49to its normal position shown in Figs. 1, 10, 12, and 13. By the time thestop pawl 49 is thus restored to its normal position, the disk 46 willhave carried the tail 5| of the advancing pawl 52 clockwise beyond itsupper hooked end 48, so that the latter will come to rest in a positionto intercept and be engaged by the tail 5| as the disk 46 completes arevolution and will thereby disengage the pawl 52 and ratchet I8 andstop the disk 46 at the end of its revolution. Fig. 18 shows therelative position of the parts at the end of the revolution of thetime-correcting disk.

As the time indicated by the secondary clock in Fig. 1 is ten minutesand five seconds before two o'clock and as the assumed standard time isthe fifty-ninth minute at the moment of releasing of the disk 46, thetime-correcting disk during its minute of rotation, the sixtieth minute,advances the time setting of the clock to two o'clock and releases theclock for normal cpLration exactly at the end of the sixtieth minute.with the result that the time indicated by the secondary clock will thenbe coincident with the standard time source.

As explained previously, the stop pawls l2 and 13 are moved into theirrespective intercepting positions as soon as the disk 46 begins torotate, and also the disk 46 rotates at the speed of the seconds gear22, thereby requiring one minute to complete its revolution. Thus, withthe secondary clock at the time position indicated in Fig. 1, when thedisk 46 commences to rotate at the beginning of the sixtieth minute, thestop pawl 12 will immediately move into blocking position and will stopthe arm 29 and seconds hand I 2 when the latter reaches the even minuteor sixty-second position. The stop pawl 13 will also immediately moveinto its intercepting position. As the disk 46 rotates at the speed ofthe seconds gear 22, the advancing stud 61 carried thereby will moveclockwise an angular distance equal to a fraction more'than fiftyseconds before engaging the outer edge 4| of the spring finger 36 on theminutes gear 36. The parts are shown in Fig. 12 in their relativepositions at the moment the stud 61 engages the end of the finger 36.The stud 61 will then rotate the minutes gear 36 and minutes hand l3clockwise at the same speed as the seconds gear 22 for the remainingportions of the sixtieth minute. As explained, the tail 5| of theadvancing pawl 52 strikes the hooked end 48 of the stop pawl 49 at theend of the revolution of the disk 46, and thereby disconnects the disk46 from the seconds gear 22 and st )ps the disk 46. Simultaneouslytherewith, the wedge-shaped end 51 of the lever 55 enters the notch 56and thereby moves the stop pawls I2 and 13 back to their normalpositions so as to release the stop arm 29 and stud 31. The constructionis such that the latter occurs exactly at the end of the sixtieth minuteso that the hands l2 and I3 will then indicate the correct time as theycommence rotating. The relative position of the parts at the moment thedisk 46 stops rotating and the arm 29 and stud 31 are released, is shownin Fig. 13.

The foregoing describes the time-correcting operation when the secondaryclock is slow with respect to standard time at the fifty-ninth minute.If the secondary clock indicates the correct time at the fifty-ninthminute the relative position of the parts when the disk 46 is releasedis as follows: the outer edge 4| of the spring 38 will be at achronological position just one minute short of clearing the forwardedge of the advancing stud 61, so that the stud 61 will make itsrevolution with the disk 46 while the edge 4| ismoving an angulardistance equal to one minute and will just engage the edge 4| at the endof the sixtieth minute when the disk 46 comes to rest. Also, with theclock indicating correct time at the fifty-ninth minute, the stop arm 29will be short of the intercepting position of the stop pawl 12 by theangular distance the arm 25 will travel in one second, and the leadingface of stop stud 31 will be short of the intercepting position of thestop pawl 13 by the angular distance the stud 31 will travel in oneminute. The construction is such that the pawls 12 and 13 will reachtheir intercepting or blocking positions when the disk 46 has beenrotated slightly more than one second. Consequently, when the clock ison time, pawl 12 will move into blocking position just as the secondsstop arm 29 moves underneath the pawl 12 and past the blocking positionand the pawl 12 will move out of blocking position and release the arm29 exactly on the even minute. When the pawl 13 moves into its blockingposition the forward face of the minutes stop stud 31 will be short ofthe pawl I3 by the amount it will travel in approximately fifty-nineseconds, and the pawl '13 moves out of its blocking position to releasethe minutes stud and gear exactly on the even hour.

From the foregoing, it is apparent that the clock construction disclosedherein will also correct itself when the clock is fast by less than aminute at the moment the standard time signal is received. This amountof correction for running fast is considered ample in a clock driven bya synchronous motor as the controlled frequency at power stations isalways kept within a closer range than one minute. In case the clock isrunning fast by a fraction of a minute at the moment the signal isreceived, the stop pawl 13 will intercept and stop the stud 31 uponreaching the even hour position and will release the stud 31 and minutesgear at the even hour, as before explained.

While there has been shown and described and pointed out the fundamentalnovel features of the invention as applied to a single modification, itwill be understood that various omissions and substitutions and changesin the form and details of thedevice illustrated and in its operationmay be made by those skilled in the art without departing from thespirit of the invention. It is the intention therefore to be limitedonly as indicated by the scope of the following claims.

What is claimed is:

1. In time-keeping apparatus, the combination of a driving motor adaptedto operate continuously at a uniform time rate; a time member mountedfor rotation about a given axis; clockdriving means connecting saidmotor and said time member for normally driving the later at a uniformtime-keeping rate; a clock-advancing member adjacent said time memberand being rotatable about the same axis as the latter; a one-waycoupling comprising a first coacti part secured to and rolatable withsaid time member and a second coacting part secured to and rotatablewith said clock-advancing member and said coupling parts being movablein approximately the same circular path and being constructed so thatsaid first part may move clockwise past said second part withoutaffecting the condition of relative movement of said members and so thatsaid second part, when moving clockwise at a faster rate than said firstpart and upon overtaking said first part, engages and drives said firstpart and time member at the rate of said clock-advancing member; meansnormally holding said clock-advancing member stationary in apredetermined angular position; signal-responsive means adapted to beoperated by a signal transmitted at a predetermined instant withreference to standard time for rendering said holding means inoperative;motiontransmitting means including clutch mechanism also operable underthe control of said signalresponsive means for connecting said motor andsaid clock-advancing member to rotate the latter from is normal angularposition throughout one complete revolution, said motion-transmittingmeans and holding means cooperating after completion of one revolutionof the clockadvancing member to disconnect the clock-advancing memberfrom the motor and thus terminate further rotation of theclock-advancing member, said clock-advancing member being operable uponrotation thereof when said iime member is at a chronological positionlater than the standard time position to cause said second coacting partto overtake and engage said first coacting part on the time member toadvance the latter to a chronological position coincident with standardtime at the moment said motor and clock-advancing member becomedisengaged at the end of one complete revolution of the latter.

2. In time-keeping apparatus, the combination 11 of a driving motoradapted to operate continuously at a uniform time rate; a rotatableminutes member; yieldable friction means operatively connecting saidmotor and minutes member for driving the latter at its normaltime-keeping rate 01' one R. P. 3.; a clock-advancing member arrangedadjacent to and supported for rotation about the same axis as saidminutes member; releasable means normally holding said clock-advancingmember stationary and in a predetermined angular position;motion-transmitting means including a one-revolution clutch operable toconnect said motor and said clockadvancing member for rotating thelatter for one revolution at the rate oi one R. P. M. and to disconnectsaid motor and clock-advancing mem ber upon the latter being restored toits said normal angular position; said holding means normallymaintaining said one-revolution clutch inoperative; means responsive tothe reception 01' a signal at a predetermined standard time forreleasing said holding means to permit said clutch to become effective;and coupling means between said clock-advancing and minutes members andoperable, when said minutes member is at a chronological position slowerthan standard time and upon operation of said clutch, to drive saidminutes member clockwise by said clockadvancing member and at the rateof the latter and for an angular distance sufficient to advance theminutes member to a chronological position coincident with standard timeat the end of the single complete revolution of said clock-advancingmember.

3. In time-keeping apparatus, the combination of a driving motor adaptedto operate continuously at a uniform time rate; a rota.ablesecondslmember; means operatively connecting said seconds member anddriving motor for driving the former at its normal time-keeping rate ofone R. P. M.; a seconds stop element secured to and rotatable with saidseconds member; a rotatable minutes member; means operatively connectingsaid minutes member and driving motor for driving the former at itsnormal time keeping rate of one R. P. H.; a clock-advancing memberarranged adjacent to and supported for rotation about the same axis assaid minutes member; releasable means normally holding saidclock-advancing member stationar in a predetermined angular position;motion-transmitting means including a one-revolution clutch operable toconnect said motor and said clock-advancin: member for rotating thelatter through one complete revolution at the rate of one B. P. M. andto disconnect said motor and clock-advancing member upon the latterbeing restored to its said normal angular position; said releasableholding means also normally maintaining said clutch inoperative; meansresponsive to the reception of a signal at a predetermined standard timefor releasing said holding means to render said clutch operative;coupling means between said clock-advancing and minutes members andoperable. when said minutes member is at a chronological position slowerthan slandard time and upon operation of said clutch, for driving saidminutes member clockwise by said clock-advancing member and at the rate.of the latter and for an angular distance suiilcient to advance theminutes member to a chronological position coincident with standard timeat the end of the revolution of said clock-advancing member; and stopmeans movable when said clock-advancing member is moving away from itssaid normal angular position into blocking position with respect to saidseconds stop ele ment so that it engages and stops the latter togetherwith said seconds member at a predetermined chronological position, saidsto means being operable upon a return of said clock-advancing member toits said normal angular position to release said seconds stop elementfor normal time-keeping movement.

4. In time-keeping apparatus, the combination oi a driving motor adaptedto operate continuously at a uniform time rate; a rotatable minutesmember; clock driving means for rotating said minutes member at itsnormal timekeeping rate of one R. P. H.; a clock-advancing memberadjacent to and supported for rotation about the same axis as saidminutes member; releasable means normally holding said clockadvancingmember stationary in a predetermined angular position;motion-transmitting means including a one-revolution clutch operable tocon nect said motor and said clock-advancing member for rotating thelatter through one complete revolution at the rate of one R. P. M. andto disconnect said motor and clock-advancing member upon the latterbeing restored to its said normal angular position; said releasableholding means also normally maintaining said clutch inoperative; meansresponsive to the reception of a signal at a predetermined standard timefor releasing said holding means to render said clutch inoperative; andone-way coupling means between said minutes and clock-advancing memberspermitting the normal time-keeping movement of said minutes member whilesaid clock-advancing member occupies its said normal angular positionand providing, when said minutes member occupies a chronologicalposition later than standard time and upon operation 01' said clutch,for driving said minutes member by said clock-advancing member clockwiseat the rate of the latter and for an angular distance suflicient toadvance the minutes member to a chronological position coincident withstandard time at the end of one complete revolution oi saidclock-advancing member.

5. Time-keeping apparatus comprising in combination a motor operable ata uniform time rate; a rotatable minutes member; an abutment elementeccentrically mounted thereon and capable oi occupying chronologicalpositions with respect to an axis passing through the axis of rotation01' the minutes member; means for driving said minutes member from saidmotor at its normal time rate of one R. P. H. a clock-advancing memberdisposed adjacent to and supported for rotation about the same axis assaid minutes member: releasable means normally holding saidclock-advancing member stationary in a predetermined angular position;motiontransmitting means including a driving member operated by Saidmotor and a clutch mechanism operable to connect saiddriving member andsaid clock-advancing member to rotate the latter at the rate of one R.P. M. from its normal angular position and to disconnect said drivingmember and clock-advancing member at the end of one complete revolutionand hold the latterat its said normal angular position; means responsiveto reception oi a signal at a predetermined standard time for releasingsaid holding means to render said clutch operative; and an advancingelement fixed to said clock-advancing member and operable upon operationof said clutch mechawhen the minutes member is at a chronologicalposition later than standard time, to overtake and engage the abutmentelement on said minutes member and to thereby move the minutes member atthe rate of the clock-advancing member an angular distance sufficient toad- Vance the minutes member to a chronological position coincident withstandard time at the completion of the complete revolution of saidclockadvancing member.

6. In time-keeping apparatus, the combination of a driving motoroperable at a uniform time rate; a rotatable seconds member; a rotatableminutes member; driving means normally connecting said motor and secondsmember for rotating the latter at its normal time-keeping rate; drivingmeans connecting said seconds and minutes members for rotating thelatter at its normal time-keeping rate; a seconds stop element securedto and rotatable with the seconds member; a clock-advancing membermounted for rotation about the same axis as said minutes member andpositioned alongside thereof in close proximity thereto; releasablemeans normally holding said clock-advancing member stationary in apredetermined angular position; a oneway coupling comprising a firstcoacting part secured to and rotatable with the minutes member and asecond coacting part secured to and rotatable with said clock-advancingmember; said coupling parts being movable in substantially the samecircular path and being so constructed that said first part may moveclockwise at its normal time-keeping rate past said second part withoutaffecting the condition of relative movement of said minutes member andclockadvancing member and so that said second part, when movingclockwise at a faster rate than said first part and upon overtaking thelatter, engages and drives said first part and minutes member at thespeed of said clock-advancing member; signal-responsive means adapted tobe operated by a s gnal transmitted at a predetermined instant withreference to standard time for rendering said holding means inoperative;motion-transmitting means including clutch means responsive to thereception of a signal at a predetermined instant with respect tostandard time and operable to provide a driving connection be- I tweensaid motor and said clock-advancing member so as to rotate the latterfrom its normal angular position for a predetermined angular distanceand then being effective to disconnect said motor and clock-advancingmember, said motion-transmitting means being operable to rotate theclock-advancing member for the predetermined angular distance at a ratesuflicient, when the minutes member is slow with respect to standardtime, to effect driving engagement of said. second and first couplingpart and to advance the minutes member to a chronological positioncoincident with standard time at the moment said clutch meansdisconnects the clockadvancing member and motor; a stop member; meansoperable upon engagement of said clutch to move said stop member into ablocking position with respect to said seconds stop element and operablesimultaneously with the disconnecting 01' said clutch to move said stopmember out of blocking position to thereby release said seconds stopelement and consequently the seconds 1 member for normal time-keepingmovement.

7. In time-keeping apparatus, the combination of a driving motor adaptedto operate continuously at a uniform time rate; a time member mountedfor rotation about a given axis; a stop 14 element secured to andmovable with said time member and capable of occupying chronologicalpositions therewith; clock-driving means connecting said motor and timemember for normally driving the latter at a uniform time-keeping rate; aclock-advancing member adjacent said time member rotatable about thesame axis as the latter; a one-way coupling comprising a first coactingpart secured to and-rptatable with said time member and a secondcoacting'part secured to and rotatable with said clock-advancing member,said coupling parts being movable in approximately the same circularpath and being constructed so that said first part may move clockwisepast said second part without afiecting the condition of relativemovement of said members and so that said second part, when movingclockwise at a faster rate than .said first part and upon overtakingsaid first part, engages and drives said first part and time member atthe rate of said clock-advancing member; releasable means normallyholding said clock-advancing member stationary in a predeterminedangular position; signal-responsive means adapted to be operated by asignal transmitted at a predetermined instant with reference to standardtime for rendering said holding means inoperative; motion-transmittingmeans including clutch mechanism operable under the control of saidsignal-responsive means to connect said motor and said clock-advancingmember to rotate the latter from its said angular position for apredetermined angular distance and then to disconnect saidclock-advancing member from said motor, said motion-transmitting meansbeing operable when said clutch mechanism is effective and when saidtime member is at a chronological position later than standard time tocause clock-advancing member to move through its said predeterminedangular distance at a. rate sufilcient for said second coupling part toovertake and engage said first coupling part and to advance said timemember to a chronological position coincident with standard time at themoment said clutch mechanism disconnects said motor and clock-advancingmember; a stop member movable from a retracted position out of the pathof movement of 'said stop element to an advanced position wherein it isin said path of movement, said stop member when in its ad vancedposition being adapted to engage said stop element when the latterreaches said coincident chronological position; and means op erablesimultaneously upon initial movement of said clock-advancing member tomove said stop member into its said blocking position and operable uponthe completion of movement of said clock-advancing member for its saidpredetermined distance to move said stop member to its said normalposition.

8.- In time-keeping apparatus, the combination of a driving motoroperable at. a uniform time rate; a rotatable seconds member; meansoperatively connecting said motor and seconds member for driving thelatter at its normal timekeeping rate; a seconds stop element secured toand rotatable with said seconds member; a rotatable minutes member; aminutes stop ele ment secured to and rotatable with said minutes memberand occupying chronological positions therewith; driving meansconnecting said seconds and said minutes member for rotating the latterat its normal time-keeping rate; a clock-advancing member mounted forrotation about the same axis as said minutes member and positionedalongside thereof in close proximity thereto; releasable means normallyholding said clockadvancing member stationary in a predetermined angularposition; a one-way coupling comprising a first coacting part secured toand rotatable with the minutes member and a second coacting part securedto and rotatable with said clock-advancing member, said coupling partsbeing movable in substantially the same circular path and being soconstructed that said first part may move clockwise at its normaltime-keeping rate past said second part without affecting the conditionof relative movement of said minutes member and clock-advancing memberand so that said second part, when moving clockwise at a rate fasterthan said first part and upon overtaking the latter, engages and drivessaid first part and consequently the minutes member at the speed of saidclock-advancing member; signal-responsive means adapted to be operatedby a signal transmitted at a predetermined instant with reference tostandard time for rendering said holding means inoperative;motiontransmitting means including clutch means onerable under thecontrol of said signal-responsive means and eifective to provide adriving connection between said motor and said clock-advancing member soas to rotate the latter from its said angular position for apredetermined angular distance and thereafter being effective todisconnect said motor and clock-advancing member, saidmotion-transmitting means being opcrable when the clock-advancing memberis rotated throughout the predetermined angular distance and when saidminutes member is slow with respect to standard time, to effect drivingengagement of said second and first coupling parts and to advance theminutes member to an even hourly position coincident with standard timeat the moment said clutchmeans disconnects the clockadvancing member andmotor; a seconds stop member normally occupying an ineffective positionand movable to a blocking position where it is engaged by and stops saidseconds stop element at an even minute position; a minutes stop membernormally occupying an ineffective position and movable to a blockingposition where it is engaged by and stops said minutes stop element atsaid even hourly position; and means operable upon movement of saidclock-advancing member from its said position to move both said secondsand said minutes members to their said blocking positions and operableupon said clock-advancing member reaching the end of its movement tomove both said stop members back to their said normal positions andthereby release simultaneously said seconds member and said minutesmember.

9. In time-keeping apparatus, the combination of a driving motoroperable at a uniform time rate; a rotatable seconds member; meansoperatively connecting said motor and seconds member for driving thelatter at its normal timekeeping rate and a seconds stop element securedto and rotatable with said seconds member; a rotatable minutes member;driving means connecting said motor and said minutes member for rotatingthe latter at its normal time-keeping rate; a clock-advancing membermounted for rotation about the same axis as said minutes member andpositioned alongside thereof in close proximity thereto; releasablemeans normally holding said clock-advancing member stationary in apredetermined angular position; a one-way coupling comprising afirst-coacting part secured to and rotatable with the minutes member anda second coacting part secured to and rotatable with saidclock-advancing member, said coacting parts being movable insubstantially the same circular path and being so constructed that saidfirst part may move clockwise at its normal rate past said second partwithout affecting the condition of relative movement of said minutesmember and clock-advancing member and so that said second part, whenmoving clockwise at a rate faster than said first part and uponovertaking the latter, engages and drives said first part andconsequently the minutes member at the speed of said clock-advancingmember; signal-responsive means adapted to be operated by a signaltransmitted at a. predetermined instant with reference to standard timefor rendering said holding means inoperative; motion-transmitting meansincluding clutch means operable under the control of saidsignalresponsive means and effective to provide a driving connectionbetween said motor and said clock-advancing member so as to rotate thelatter from its said angular position for a predetermined angulardistance and then being effective to disconnect said motor andclock-advancing member, and the motion-transmitting means being operablewhen the clock-advancing member is rotated throughout the predeterminedangular distance and when the minutes member is slow with respect tostandard time,to efi'ect driving engagement of said second and firstcoacting parts and to advance the minutes member to a chronologicalposition coincident with standard time at the moment'said clutch meansdisconnects the clock-advancing member and motor; a second stop membernormally occupying an ineffective position and movable to a blockingposition where it is engaged by and stops said seconds stop element atan even minute position; and means responsive to movement of saidclockadvancing member away from its said angular position for movingsaid seconds stop member to its said blocking position and responsive tosaid clock-advancing member reaching the end of its movement for movingsaid stop member back to normal position and thereby releasing saidseconds stop element and member.

10. In time-keeping apparatus, the combination of a seconds shaft; aseconds indicating member secured to said shaft for rotation therewith;a clock driving gear mounted on said shaft; a frictional drivingconnection between said gear and shaft; 9, driving motor; meansoperatively connecting the driving motor and gear for driving the latterat a uniform time rate; 9. minutes sleeve journalled on said shaft; aminutes indicating member and a minutes gear secured to said minutessleeve and rotatable therewith; a clock driving train connecting saiddriving gear and said minutes gear for rotating the latter at its normaltime-keeping rate; a clock-advancing member mounted for rotation aboutthe same axis as said minutes gear and positioned alongside thereof;releasable means normally holding said clock-advancing member stationaryin a predetermined angular position; a one-way coupling comprising afirst coacting part secured to and rotatable with the minutes gear and asecond coacting part secured to and rotatable with said clock-advancingmember, said coupling parts being movable in substantially the samecircular path and being so constructed that said first part can moveclockwise past said second part without affecting the condition ofrelative movement of said gear and member and so that said second part,when moving clockwise at a faster rate than said first part and uponovertaking the latter, engages and drives said first part and minutesgear at the speed of said clock-advancing member; signal-responsivemeans adapted to be operated by a signal transmitted at a predeterminedinstant with reference to standard time for rendering said holding meansinoperative; motion-transmitting means including clutch means operableunder the control or said signal responsive means and efiective toprovide a driving connection between said clock driving gear and saidclock-advancing member so as to rotate the latter from its said angularposition for a predetermined angular distance and then being eflectiveto disconnect said driving gear and clock-advancing member, saidmotion-transmitting means being operable when the clock-ad-,

vancing member is rotated throughout a predetermined angular distance toefiect driving engagement of said second and first coupling parts and toadvance the minutes gear and sleeve to a chronological positioncoincident with standard time at the moment the clutch means disconnectsthe clock-advancing member and drivv ing gear.

11. Time-keeping apparatus as set forth in claim 10 including stopmeansflefiective upon operation of said clock-advancing member to moveinto blocking position with respect to the seconds stop element and tomove out of such blocking position upon disconnecting of saidclock-advancing member and driving gear.

12. In a secondary clock mechanism, a synchronously driven motor adaptedto be operated continuously according to chronological time; a rotatableseconds member and a rotatable minutes member mountedv for rotationabout a common axis; means operatively connecting each of said membersand'the driving motor in driving relationship for rotating the same atnormal time-keeping rates of one R. P. M. and one R. P. H. respectively;a clock-advancing member mounted for rotation about said common axis,disengageable means for connecting said seconds member andclock-advancing member in driving relationship for rotating the latterat the same rate as the former; coupling means between saidclock-advancing member and minutes member operable when the latter is ata chronological position slower. than standard time for driving saidminutes member at the rate of the seconds member and for an angulardistance suflicient to advance the.minutes ,member to a chronologicalposition coincident with standard time; a latch member normallymaintaining said disengageable means disengaged and maintaining saidclock advancing member stationary at a predetermined angular positionsaid latch member being operable upon tripping thereof to release saiddisengageable means, and means for tripping said latch member.

13. In a secondary clock mechanism, a synchronously driven motor adaptedto be operated continuously according to chronological time; a rotatableseconds member and a rotatable minutes member mounted for rotation abouta common axis; means operatively connecting each of relationship forrotating the same at normal time-keeping rates of one R. P. M. and oneR, P. H. respectively; a clock-advancing member mounted for rotationabout said common axis, disengageable means for connecting said 75 forrotation about the axis of rotation of said seconds member andclock-advancing member in driving relationship for rotating the latterat the same rate as the former; coupling means between saidclock-advancing member and minutes member operable when the latter is ata chronological position slower than standard time for driving saidminutes member at the rate of the seconds member and for an angulardistance sufficient to advance the minutes member to a chronologicalposition coincident with standard time; a latch member normallymaintaining said disengageable means disengaged and maintaining saidclock-advancing member stationary at a predetermined angular position,said latch member being operable upon tripping thereof to release saiddisengageable .means, and means for tripping said latch member. saidmeans comprising an electromagnetv adapted to receive an energizingsignal at'a predetermined hourly instant ottiiner 14. In a secondaryclock mechanism, a synchronously driven motor adapted to be operatedcontinuously according to chronological time; a rotatable seconds memberand a rotatable minutes member mountedtor rotation about a common axis;means operatively connecting each of said members and the driving motorin driving relationship for rotating the same at their normaltime-keeping rates of one R. P. M. and one R. P. H. respectively; theconnecting means between said minutes member comprising a friction slipdevice;;,a traction wheel mounted on said seconds member for ro a ion inunison therewith; a clock-advancing member mounted ior rotation aboutthe axis 0! rotation of said minutes and seconds members, an advancingpawl carried by said clock-advancing member; means normally urging saidadvancing pawl into engament with said traction wheel whereby saidclock-advancing member is driven by said traction wheel and at the samerate oi speed as the latter; a latch member having a part positioned inthe path of movement of said advancing pawl and adapted to engage thelatter and maintain the same disengaged from said traction wheel;coupling means between said clock-advancing member and minutes memberoperable upon engagement of the clock-advancing member by said advancingpawl for driving said minutes mem-- ber at the rate of theclock-advancing member and consequently of the seconds member for an 1angular distance sufllcient to advance the minutes member to achronological position coincident with standard time; and meansresponsive to a signal transmitted at a. predetermined hour-.

ly instant of timeior moving-said latch member out or engagement withsaid advancing pawl to:-

release the latter and establish the driving connection between saidclock-advancing member and traction wheel.

continuously according to chronological time; a rotatable seconds memberand a rotatable minutes member mounted for rotation about a common axis;means operatively connecting each of said members i'ahd the drivingmotor, in driving relationship-for rotating the same at their normaltime-keeping rates of one R. P. M. and one R. P. H. respectively; theconnecting means between said minutes member comprising a friction slipdevice; a traction wheel mounted on said. seconds "member for rotationin unison therewith; a clock-advancing member mounted 19 minutes andseconds members, an advancing pawl carried by said clock-advancingmember; means normally urging said advancing pawl into engagement withsaid traction wheel whereby said clock-advancing member is driven bysaid traction wheel and at the same rate'of speed as the latter; a latchmember having a part positioned in the path of movement ot'saldadvancing pawl and adapted to engage the latter and maintain the samedisengaged from said traction wheel; coupling means between saidclock-advancing member and minutes member operable upon engagement ofthe clock-advancing member by said advancing pawl for driving saidminutes member at the rate of the clock-advancing member andconsequently oi the seconds member for an angular distance suflicient toadvance the minutes member to a chronological position coincident withstandard timerand means for moving said latch member out of engagementwith said advancing pawl to release the latter and establish the drivingconnection between said clock-advancing member and traction wheel, saidmeans comprising a finger carried by said latch member; a trip memberhaving a shoulder thereon designed for engagement with said finger tocause release of said advancing pawl by said latch member; meansnormally urging said trip member to a position wherein said shoulder isout of engagement with said finger and said latch member is in itsoperative position; an electromagnet having an armature connected tosaid trip member, said armature being operable upon energization of saidelectromagnet to move said trip member to a position in registry withsaid finger and also being operable upon deenergization of theelectromagnet to permit said urging means to move said trip member toits normal position and in so moving cause said finger to be engaged bysaid shoulder to release said latch member.

16. In a secondary clock mechanism a synchronously driven motor adaptedto be operated continuously according to chronological time; a

rotatable seconds member and a rotatable minutes member mounted forrotation about a common axis; means operatively connecting each of saidmembers and the driving motor in driving relationship for rotating thesame at their normal time-keeping rates of one R. P. M. and one R. P. H.respectively; the connecting means between said minutes member and themotor being a friction slip device; a traction wheel mounted on saidseconds member for rotation in unison therewith; a clock-advancingmember mounted forrotation about the axis of rotation of said minutesand seconds members, an advancing pawl carried by said clock-advancingmember; means normally urging said. advancing pawl into engagement withsaid traction wheel whereby said clock-advancing member is driven bysaidtraction wheel and at the same rate of speed as the latter; a latchmember having a part positioned in the path of movement of saidadvancing ram and adapted to engage the latter and maintain the samedisengaged from said traction wheel: coupling means between saidclock-advancing member and minutes member operable upon engagement ofthe clock-advancing member by said advancing pawl for driving saidminutes member at the rate of the clock-advancing member andconsequently of the seconds member for an angular distance suificient toadvance the minutes member to a chronological position coincident withstandard time; means tor moving said latch member out of engagement withsaid advancing pawl to release the latter and establish the drivingconnection between said clock-advancing member and traction wheel, saidmeans comprising a finger carried by said latch member; a trip memberhaving a shoulder thereon designed for engagement with said finger tocause release of said advancing pawl by said latch member; meansnormally urging said trip mem ber to a position wherein said shoulder isout of engagement with said finger and said latch member is in itsoperative position; an electromagnet having an armature connected tosaid trip member, said armature being operable upon energization of saidelectromagnet to move said trip member to a position in registry withsaid finger and also being operable upon deenergization of theelectromagnet to permit said urging means to move said trip member toits normal position and in so moving cause said finger to be engaged bysaid shoulder to release said latch member; and cam means operable upondeenergization of said electromagnet for moving said trip member andshoulder out of engagement with said finger to permit said latch memberto be moved toits normal operative position.

- REYNOLD B. JOHNSON.

EDWARD F. GEIGER.

REFERENCES CITED The following references are of record in the

